Check valve assembly

ABSTRACT

A check valve may include a housing having a bore therethrough, the bore including an inner surface and a bearing face; a check seat adaptor coupled to the housing; a seal in the housing, the seal including a seat bore; and a dart disposed in the bore between the seal and the bearing face and axially moveable between closed and open positions. The dart may include a tail and a head that has at least one dart inlet and sealingly engages the seal when the valve is closed. The tail defines an inner chamber having an outlet that is in fluid communication with the bore. The dart inlet(s), the inner chamber, and the outlet may be in fluid communication and together define a dart flow path through the dart. A biasing device may urge the dart toward the seal.

CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY CLAIM

This application is a continuation of application Ser. No. 16/985,439filed Aug. 5, 2000, which is a non-provisional application that claimspriority from U.S. provisional application No. 62/892,121, filed Aug.27, 2019.

TECHNICAL FIELD/FIELD OF THE DISCLOSURE

The present disclosure relates generally to apparatus and methods foruse in hydraulically fracturing subsurface formations.

BACKGROUND OF THE DISCLOSURE

In unconventional hydrocarbon production, the rate of production mayfluctuate over both long and short time spans. For example, a well mayproduce at extremely high rates when initially completed and thendeplete rapidly. When the natural drive energy of a reservoir is notstrong enough to push oil to the surface, artificial lift may be used tolift produced fluids to the surface. While there are various ways toachieve artificial lift, gas lift is an increasingly common artificiallift choice because of its flexibility.

In gas lift wells, a compressed gas is injected into the well. Theinjected gas decreases the viscosity of the fluids in the well andreduces the hydrostatic pressure at the bottom of the well by displacingsome of the well fluids, which allows the produced fluids to flow moreeasily to the surface and allows reservoir fluids to enter the well at ahigher flow rate. In some cases, the gas to be injected into theproduction tubing is conveyed downhole via the annular space surroundingthe production tubing and enters the production tubing through one ormore gas lift valves. Each gas lift valve may include a check valve toselectively allow a fluid flow from the inlet side of the check valve tothe outlet side of the check valve and prevent reverse flow from thetubing to the annulus.

By way of example, FIG. 1 schematically depicts a gas lift system 10that includes a production tubing 14 that extends into a wellbore. Anannulus is defined between the production tubing and the wellbore, whichmay or may not be cased. The production tubing 14 has a centralpassageway 17. The system may include a gas compressor 12 located on thesurface. The compressor provides pressurized gas to the annulus 15. Tocontrol the communication of gas between the annulus 15 and the centralpassageway 17 of the production tubing 14, the system may includeseveral side pocket gas lift mandrels 16, as shown at 16 a, 16 b and 16c. Each of the gas lift mandrels 16 may include an associated gas liftvalve 18, as shown in phantom at 18 a, 18 b and 18 c. The gas liftvalves 18 each establish a one-way fluid flow path from the annulus 15to the central passageway 17.

As wells age and it becomes desirable to using more aggressive gas lifttechniques, check valves are subjected to greater fluid flow rates andmore rapid cycling rates, both of which may reduce the lifespan and/orefficacy of a check valve.

SUMMARY

A check valve may comprise a check housing having a housing boretherethrough, the housing bore including an inner surface and defining ahousing bearing face; a check seat adaptor mechanically coupled to thecheck housing and including a check seal in the housing bore, the checkseal including a seat bore; and a check dart disposed in the housingbore between the check seal and the housing bearing face and axiallymoveable therein between a closed position and an open position. Thecheck dart may include a head portion having a largest head diameter,the head portion configured to sealingly engage the check seal when thecheck dart is in the closed position, the head portion including atleast one dart inlet, a tail portion having an outside dart diameterthat is smaller than the largest head diameter, the tail portiondefining an inner chamber having a chamber outlet that is in fluidcommunication with the housing bore, and a biasing shoulder between thehead portion and the tail portion, wherein the shoulder is oriented awayfrom the check seal. The dart inlet(s), the inner chamber, and thechamber outlet may be in fluid communication and may together define adart flow path through the check dart. The check valve may also includea biasing device compressed between the biasing shoulder and the housingbearing face so as to urge the check dart toward the check seal.

The biasing device may not be in the dart flow path. An annular spacemay be defined between the tail portion and the housing and the biasingmeans may be disposed in the annular space. The tail portion may includeat least one port that provides fluid communication between the innerchamber and the annular space.

The housing bore may include a box section, a valve section, a landingsection, and an outlet section. A portion of the tail portion may beslidably received in the landing section. The housing bearing face mayextend radially between the valve section and the landing section and alanding face may extend radially between the landing section and theoutlet section. The tail portion of the dart may seat on the landingface when the check dart is in a fully open position. The housing boremay further include a retainer lip extending radially between the boxsection and the valve section.

The head portion of the dart may include at least two or more dartinlets. In some embodiments, the head portion of the dart may includefive circumferentially-spaced dart inlets. At least one dart inlet mayinclude a radial component.

The outlet of the inner chamber may be aligned with the housing bore.The dart(s) may have a cross-sectional area. A cross-sectional area ofthe dart flow path may include the sum of the dart inlet cross-sectionalareas. The smallest cross-sectional area of the dart flow path may begreater than the cross-sectional area of the seat bore. The dart(s) mayhave a minimum cross-sectional area and the sum of the dart inletminimum cross-sectional areas may be equal to or greater than thecross-sectional area of the inner chamber.

The smallest cross-sectional area of the inner chamber may be equal toor greater than the largest cross-sectional area of the seat bore. Thedart flow path may include no portion having a center line that forms anangle greater than 60 degrees with respect to the axis of the checkvalve.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale. In fact, the dimensions of the variousfeatures may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic diagram of a gas lift system in a well;

FIG. 2 is a schematic cross-section showing a check valve in accordancewith one embodiment of the present disclosure;

FIG. 3 is an end view of a check dart in accordance with one embodimentof the present disclosure; and

FIG. 4 is cross-section taken along lines 4-4 of FIG. 3 .

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof various embodiments. Specific examples of components and arrangementsare described below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.Further, in the description that follows, because the device is a checkvalve adapted to allow fluid flow in only one direction, and for thesake of clarity, the terms “upstream” and “downstream” will be used torefer to positions relative to the intended direction of fluid flow,which is generally to the right as drawn.

Referring to FIG. 2 , an embodiment of a check valve 20 may includecheck seat adaptor 22, check housing 25, moveable check dart 30, andbiasing device 50 that urges the check dart 30 into a closed position.Check seat adaptor 22 may include an adaptor body having a longitudinalseat bore 21 therethrough. Check housing 25 may include box 23 and pin27 and may include a longitudinal stepped bore 60. Pin 27 may include anengagement portion such as, for example, threads 68, for engaging anadjacent tubular.

Stepped bore 60 of check housing 25 may include a box section 60 a,valve section 60 b, landing section 60 c, and outlet section 60 d. Ofsections 60 a-d, box section 60 a has the largest diameter. Valvesection 60 b is defined by an inside wall of box 23. Outlet section 60 dis defined by an inside wall of pin 27 and has a diameter that is lessthan the diameter of valve section 60 b. Landing section 60 c is betweenvalve section 60 b and outlet section 60 d and may be located in pin 27(as shown), or in box 23. Landing section 60 c may have a diameter thatis less than the diameter of valve section 60 b and greater than thediameter of outlet section 60 d.

Box section 60 a may include a means for mechanically engaging checkseat adaptor 22 such as, for example, threads 62. Check housing 25 mayinclude retainer lip 61 defined between box section 60 a and valvesection 60 b, spring seat 54 defined between valve section 60 b andlanding section 60 c, and dart seat 59 defined between landing section60 c and outlet section 60 d.

Seal 24, such as an O-ring seal, may be disposed between check seatadaptor 22 and box section 60 a. Check seal 26 and check seal retainer28 may be retained between check seat adaptor 22 and retainer lip 61.Check seal 26 may be annular and may define a sealing surface 41 havingan opening therethrough. The opening in check seal 26 may be at least aslarge as the seat bore 21. To facilitate sealing, check seal 26 andcheck seal retainer 28 may each include an elastomeric material or anyother desired material.

Referring now to FIGS. 1-3 , check dart 30 may include head portion 32and tail portion 34. Head portion 32 and tail portion 34 may or may notbe integrally formed. Head portion 32 includes a nose 35. Nose 35 may beconfigured to guide check dart 30 as check dart moves into sealingengagement with check seal 26 (to the left as drawn). In certainnon-limiting embodiments, nose 35 may be conical or hemispherical.Adjacent to nose 35 is sealing shoulder 38. Sealing shoulder 38 has adiameter greater than that of nose 35 and is configured to bear on andform a seal with sealing surface 41 of check seal 26. The diameter ofhead portion 32 increases from sealing shoulder 38 to a head diameter Dhthat is nearly as great as the diameter of valve section 60 b butsufficiently smaller to allow reciprocating movement of check dart 30within check housing 25.

Tail portion 34 of check dart 30 may be tubular and may have an outsidediameter Dt that is smaller than Dh (FIG. 4 ). The interface betweenhead portion 32 and tail portion 34 defines biasing shoulder 52 that isoriented away from check seal 26. Annular space 55 (FIG. 2 ) is definedbetween the outside of tail portion 34 and the inside surface of valvesection 60 b. Tail portion 34 includes annular wall 31 that definesinner chamber 37. The smallest cross-sectional area of inner chamber 37may be equal to or greater than the largest cross-sectional area of seatbore 21. Inner chamber 37 includes outlet 39 that opens into steppedbore 60 of check housing 25. Annular wall 31 may include one or moreports 58 therethrough that allow fluid communication between innerchamber 37 and annular space 55.

Head portion 32 of check dart 30 may include one or more dart inlets 43and may include two or more dart inlets 43. Each dart inlet 43 providesa fluid flow path from the outside of head portion 32 to inner chamber37. Each dart inlet 43 may have inlet opening 42 and outlet opening 44.In the illustrated embodiment, there are five dart inlets 43; in someembodiments, there may be more or fewer dart inlets 43. By way ofexample only and not limitation, the number of dart inlets 43 may be anynumber from one to twenty. In embodiments where there is more than onedart inlet 43, the dart inlets may be evenly spaced about thecircumference of head portion 32 and may be positioned in two or morelongitudinally-spaced rows. Dart inlet openings 42 may be positioneddownstream of sealing shoulder 38 so as to avoid interfering with thesealing function of check dart 30.

In some embodiments, each dart inlet 43 may comprise a bore havingcenterline CLb. Because at least a portion of each inlet opening 42 maybe at a greater radius from the tool axis than radius of inner chamber37, the direction of each dart inlet centerline may have a radialcomponent. Thus, in longitudinal cross-section (FIGS. 2 and 4 ), eachCLb may define an angle a between 20 and 80 degrees with thelongitudinal axis of check dart 30. In some embodiments, a may bebetween 30 and 50 degrees. In some embodiments and as best seen in FIG.3 , each dart inlet 43 may have a non-circular cross-section; in theillustrated embodiment, the circumferential extent of each dart inletbore is greater than its radial extent. In the illustrated embodiment,each dart inlet 43 is shown as substantially straight but in otherembodiments, dart inlets 43 could be configured differently.

In some embodiments, the components of check valve 20 are configured sothat the pressure drop across the valve when the valve is in its openposition is minimized. Thus, in some embodiments, each dart inlet has aminimum cross-sectional area (measured normal to the direction of flow)and the sum of the dart inlets' minimum cross-sectional areas at anypoint along check valve 20 may be equal to or greater than thecross-sectional area of seat bore 21. In some embodiments, thecross-sectional area of inner chamber 37 may be equal to or greater thanthe cross-sectional area of seat bore 21. In some embodiments, the sumof the dart inlets' minimum cross-sectional areas may be equal to orgreater than the cross-sectional area of inner chamber 37. Likewise, thefluid flow path(s) through the valve may be configured to avoid one ormore of: obstructions, changes in flow direction, edges, corners, andother features that may increase turbulence.

The downstream end of tail portion 34 may be sized to be slidablyreceived in landing section 60 c of check housing 25. In someembodiments, the disposition of tail portion 34 in landing section 60 chelps maintain check dart 30 in coaxial alignment with check housing 25as check dart 30 moves within check housing 25. Tail portion 34 andlanding section 60 c may be configured such that dart seat 59 limitsmovement of check dart 30 in the downstream direction. In someembodiments, check dart 30 may seat on dart seat 59 when check valve 20is fully open. Ports 58 are provided to allow fluid equilibrationbetween inner chamber 37 and annular space 55 but annular space 55 isnot part of the primary fluid flow path through check valve 20.

In some embodiments, including the embodiment illustrated in FIG. 2 ,tail portion 34 and landing section 60 c may be configured such thatports 58 are blocked by check housing 25 when check dart 30 is seated ondart seat 59 and are not blocked when check dart 30 engages check seal26. In instances in which ports 58 can be blocked, fluid equilibriumbetween inner chamber 37 and annular space 55 may be hindered, which mayproduce a delaying or damping effect on operation of check valve 20. Insome instances, a delaying or damping effect could be advantageous inreducing or preventing “chattering” of the dart, i.e. where the dartcycles between open and closed relatively rapidly. Chattering mayincrease wear, shorten the lifespan, and reduce the efficacy of checkvalve 20.

In other embodiments, tail portion 34 and landing section 60 c may beconfigured such that ports 58 are not blocked when check dart 30 isseated on dart seat 59 or when check dart 30 engages check seal 26.

As illustrated, in some embodiments, biasing device 50 may be coilspring 51 positioned in annular space 55, with an upstream end of spring51 configured to bear on biasing shoulder 52 and a downstream end ofspring 51 configured to bear on spring seat 54. Biasing device 50 may bea coil spring, as shown, or may be any other suitable mechanism forapplying a biasing force to check dart 30, including but not limited to:other spring configurations, hydraulic or pneumatic devices, elastomericmembers in compression or tension, or the like. In some embodiments,biasing device 50 may be partially compressed when check valve 20 isclosed and further compressed when check valve 20 is open so thatbiasing device 50 applies a biasing force that urges check dart 30 inthe upstream direction regardless of the position of check dart 30within check valve 20. In these embodiments, the length of biasingdevice 50 may be somewhat greater than the maximum longitudinal distancebetween biasing shoulder 52 and spring seat 54, i.e. measured when checkvalve 20 is closed and check dart 30 is in sealing engagement with checkseal 26.

In some embodiments, biasing device 50 may be configured such thatmaximal compression of biasing device 50, i.e. when check valve 20 isfully open, does not cause plastic deformation of biasing device 50.Likewise, nose 35 may be configured such that when the tubing pressureor flow rate falls below a certain level and check valve 20 is fullyclosed, nose 35 engages check seat adaptor 22. The metal-to-metalengagement of nose 35 with check seat adaptor 22 may provide someadditional sealing capability and may serve to prevent check seal 26from being crushed and destroyed. The engagement of nose 35 with checkseat adaptor 22 may provide a “positive stop” that may extend the lifeof check seal 26.

As described above, in the absence of elevated fluid pressure in seatbore 21, check valve 20 may be normally closed. In operation, when thereis sufficient fluid pressure in seat bore 21 to overcome the biasingforce of biasing device 50, check dart 30 will shift in the downstreamdirection, thereby allowing fluid to pass between nose 35 and check seal26. Fluid flowing past nose 35 will flow through dart inlet(s) 43 intoinner chamber 37, out of inner chamber 37 via outlet 39, and into outletsection 60 d of bore 60.

Because the fluid flow path through check valve 20 passes through theinterior of check dart 30, whereas biasing device 50 is in annular space55, biasing device 50 is not generally exposed to the fluid flow whencheck valve 20 is open. As a flowing fluid may erode equipment withwhich it comes in contact, removing biasing device 50 from the fluidflow path may extend the life of biasing device 50. In addition, becausefluid flowing though check valve 20 need not flow through or alongbiasing device 50, the fluid flow path may be less turbulent, and mayresult in a smaller pressure drop across check valve 20. Annular space55 is not part of the primary fluid flow path through check valve 20.

In an exemplary application, if check valve 20 is installed as a gaslift valve 18 as illustrated in FIG. 1 , check valve 20 may be installedwhen no lift gas is being delivered. In some embodiments, check valve 20is normally closed and the production tubing pressure in acting on theback (downstream) side of check valve 20 may be greater than the annulusor casing pressure acting on the front (upstream) side. By contrast,when compressed gas is pumped into the annulus 15, the annulus or casingpressure may increase relative to the production tubing pressure. Theincreased annulus pressure will exert a force on the front side of checkvalve 20. If sufficient, the increased annulus pressure will overcomethe force applied by biasing device 50 and check dart 30 will retractfrom check seat adaptor 22 and check seal 26 as biasing device 50 iscompressed, thereby opening check valve 20. The opening of check valve20 permits gas to flow from the annulus through the gas lift valve 18and into the production tubing 14.

In some embodiments, biasing device 50 may be omitted from check valve20. In such embodiments, sometimes referred to as upside-downinstallations, the check valve may be installed such that that the forceof gravity tends to urge check dart 30 onto dart seat 59. Regardless ofthe orientation of check valve 20 (right-side-up or upside-down),biasing device 50 may not be needed if fluid velocity is sufficient.

As the pressure drop across a valve is a function of the conditions inwhich it is operated, including for example, fluid velocity, fluidviscosity, and pressures upstream and downstream of the valve, thepressure drop across check valve 20 will depend on its operatingconditions

The check valves disclosed herein may be advantageously deployed in oneor more side pocket gas lift mandrels. In other embodiments, the checkvalves disclosed herein may be used to limit the direction of flow ofother fluids.

By way of example only, check valve 20 may be included in a gas liftapparatus positioned between the well annulus and the inside of aproduction tubing in a hydrocarbon-producing well. In some embodiments,the gas lift apparatus would include a gas lift valve that includes acheck valve 20. Check valve 20 would selectively allow fluid flow froman inlet side of the check valve to an outlet side of the check valvewhen open and may be biased to prevent leakage from the outlet side tothe inlet side of the check valve when closed.

The foregoing outlines features of several embodiments so that a personof ordinary skill in the art may better understand the aspects of thepresent disclosure. Such features may be replaced by any one of numerousequivalent alternatives, only some of which are disclosed herein. One ofordinary skill in the art should appreciate that they may readily usethe present disclosure as a basis for designing or modifying otherprocesses and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein. Oneof ordinary skill in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. A check valve adapted for use in an oil and gas well, comprising: ahousing having a housing flow path between a first end and a second endof the housing; a dart positioned in the housing flow path and adaptedto move between at least: (1) a first position in which the dartsubstantially blocks a portion of the housing flow path, and (2) asecond position in which the dart does not block the portion of thehousing flow path; the dart further including a dart flow path between afirst end and a second end of the dart; the dart further including aplurality of inlet ports in fluid communication with the housing flowpath and the dart flow path; a biasing device for retarding movement ofthe dart between its first position and its second position, wherein thebiasing device is positioned in the housing flow path but not the dartflow path; whereby, when the dart is in its second position, the checkvalve is configured such that flow travels through the housing flow pathat the first end of the housing, the plurality of ports in the dart, thedart flow path, and the housing flow path at the second end of thehousing.
 2. The check valve of claim 1 wherein the housing includes acheck housing and a check seat adaptor, wherein said check housing isconnected to said check seat adaptor.
 3. The check valve of claim 2wherein the dart includes a longitudinal axis and one or more of theplurality of dart inlet ports includes a centerline, wherein thecenterline of the one or more plurality of dart inlet ports forms anangle with the longitudinal axis of the dart.
 4. The check valve ofclaim 3 wherein the dart further includes at least one outlet portconfigured to allow fluid communication between the dart flow path andthe housing flow path.
 5. The check valve of claim 4 wherein the outletport is open to fluid communication between the dart flow path and thehousing flow path when the dart is in its first position.
 6. The checkvalve of claim 5 wherein the outlet port is closed fluid communicationbetween the dart flow path and the housing flow path when the dart is inits second position.
 7. The check valve of claim 6 wherein the dartincludes a biasing shoulder configured to receive a first end of thebiasing device.
 8. The check valve of claim 7 wherein the housingincludes a seat configured to receive a second end of the biasingdevice.
 9. The check valve of claim 8 wherein the housing includes adart seat configured to receive the second end of the dart when the dartis in its second position.
 10. The check valve of claim 9 wherein thedart includes a region having a head diameter and a region having a taildiameter, where the head diameter is larger than the tail diameter. 11.The check valve of claim 10 wherein the biasing device is located in theregion having the tail diameter.
 12. A check valve, comprising: a darthaving an inner chamber; the dart adapted to move between at least afirst position in which the dart substantially blocks a flow path in thecheck valve and a second position in which the dart does not block theflow path in the check valve; the dart including at least one inletopening, wherein the inlet opening has a centerline at an angle with alongitudinal axis of the check valve.
 13. A check valve, comprising: abore; a dart positioned within the bore and adapted to move between atleast a first position in which the dart substantially blocks the boreand a second position in which the dart does not block the bore; abiasing device for retarding movement of the dart between its firstposition and its second position, wherein the biasing device ispositioned on an outside surface of the dart substantially free of flowin the bore.